v1.91.359.0 feat(verify): /verify skill and gstack-checks bin (GST-116 PR 1) (#3672)

* verify: add /verify skill and gstack-checks (GST-116 PR 1)

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* fix: pre-landing review fixes

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* fix: pre-landing review fixes (pass 2)

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* fix: adversarial review fixes

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* fix: win32 NUL discard for the Go build check; unique Health Stack names (rule 23 grant)

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* docs: changelog fragment for /verify

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gstack/llms.txt

@@ -71,6 +71,7 @@ Conventions:
 - [/test-audit](test-audit/SKILL.md): Find low-value or duplicate tests and the test-only code they keep alive.
 - [/ubicloud](ubicloud/SKILL.md): Run a heavy suite, build or eval on an ephemeral 16-vCPU Ubicloud VM: TTL-named VMs, a reaper, quota preflight and a hang watchdog.
 - [/unfreeze](unfreeze/SKILL.md): Clear the freeze boundary set by /freeze, allowing edits to all directories again.
+- [/verify](verify/SKILL.md): Build loop while coding: run the repo's checks and the tests /ship would pick, fix, repeat until green.
 - [/write-skill](write-skill/SKILL.md): Write a new agent skill or improve one without bloat: the edit ladder, levels, drift and size checks, full diets.
 
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